Pathogenic bacterial contamination in products not only puts the public at risk, but also is costly because of routine product testing, product recalls and liabilities. When responding to incidents of food contamination or other bacteriological contamination, the speed and accuracy of the identification of the organism can be of importance. At present, typical systems and methods of making such identification include polymerase chain reaction (PCR), or antibody-based techniques, which require complicated sample preparation in order to achieve reliable results.
Traditional methods for detection and identification of bacterial contaminants, such as Listeria monocytogenes, usually take 24-48 h following the growth of bacteria on an agar plate or in a culture broth, owing to the extent of biochemical or molecular testing required for confirming the identity of the culture. Nucleic acid or antibody-based methods have been successful and are used for pathogen detection by some large food manufacturers and by regulatory agencies. However, the ability of these methods to differentiate live from dead bacteria and specificity of different strains of closely related species, such as Listeria, are of concern.
Another commonly used method for bacterial detection is the classical culture method where test samples are enriched and plated on agar plates for identification of individual colonies by biochemical or serological assays. The assays for identification of the bacterial colonies require multiple steps, use sophisticated and expensive molecular tools and require a skilled technician to perform the tests.